Optical fiber rearrangement method and device

ABSTRACT

The present invention provides an optical interconnection device whereby arrays of fibers or waveguides arranged in a given orientation at an input side are rearranged in a three-dimensional rearrangement area within the device and exit at an output side arranged in a different orientation from the input side. Distinct arrays are created at the output side via manual or automated placement based on a roadmap.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.09/597,324, filed Jun. 19, 2000 now U.S. Pat. No. 6,464,404.

BACKGROUND

This invention is related to fiber optic communications and moreparticularly to an optical fiber interconnection device and method forrearranging arrays of optical fibers between an input side and an outputside.

The use of fiber optics for high speed communications is findingincreased use within large microprocessors and multiple microprocessorsystems. For example, in optical switches more and more channels areneeded for transmission of data. In back planes, more opticalinterconnections are required as more daughter cards are added forincreasing the number of channels. Cross connects may also be utilizedwithin back planes for communicating between groups of daughter cards ormicroprocessors. These applications typically require that each daughtercard or microprocessor be in communication with each of the otherdaughter cards or microprocessors in the system. These communicationsare achieved by connecting optical fibers in a point to point fashionbetween each daughter card or microprocessor and the other daughtercards or microprocessors in the system. It can therefore be appreciatedthat as the number of channels required is increased, the number ofdaughter cards or microprocessors that must communicate with each otheris also increased. This creates a problem in that point to point wiringfor large numbers of channels is labor intensive, costly, timeconsuming, and susceptible to connection errors. Additionally, becauseoptical fibers are subject to environmental limitations such as bendradius, fiber management systems are often employed for such largesystems of interconnections. Fiber management becomes a challengingproblem as a number of channels and the number of point to pointconnections are increased resulting in higher fiber counts in thebackplane.

In one known prior art system of backplane fiber optic interconnections,a single optic fiber is arranged in a desired pattern on atwo-dimensional adhesive coated substrate in a controlled manner. Theoptic fiber is arranged to maintain a minimum bend radius in a twodimensional plane of 25 mm, which is a typical minimum to prevent damageto the fibers. After testing the single optic fiber, the substrate andoptic fiber are cut at one or more locations to form an opticalbackplane interconnect with a desired routing pattern. However, all ofthe optic fibers are bonded in position requiring additional opticalfiber ribbons to make the backplane connections to the printed circuitboards, creating additional optic interfaces which are subject toadditional signal losses.

SUMMARY

The present invention addresses these problems by providing an opticalinterconnection device whereby arrays of fibers arranged in a givenorientation at an input are rearranged within the device and exit at anoutput arranged in a different orientation from the input. A method ofaccomplishing the rearrangement is to first provide a plurality of fiberarrays each containing a plurality of individual fibers. Thisarrangement is then fixed at an output side utilizing a suitable methodsuch as an adhesive to form a bundle. The bundle of fibers at the outputis then separated, either through an automated or manual process, in adifferent orientation, for example in a direction orthogonal to eachfiber array at the input. Distinct ribbons or arrays are created at theoutput by the separating operation.

In another aspect, the present invention provides a method of creatingan optical fiber interconnection in which arrays of optical fibers areprovided. The matrix holding each of the arrays of optical fiberstogether is partially stripped or leached away at one end of the array.The stripped optical fibers are then rearranged in three-dimensionalspace into separate output arrays using a manual or automated processbased on a desired optic fiber roadmap and bonded or adhered together toform the output arrays of the optical fiber rearrangement device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference tothe accompanying figures of which:

FIG. 1 is a schematic diagram of a representative four by fourrearranging device according to the present invention;

FIG. 2 is a three dimensional view of the input and output of the deviceof FIG. 1;

FIG. 3 is a three dimensional view of the device of FIG. 1 during anintermediate assembly step;

FIG. 4 a cross-sectional view of an enclosure containing the device ofFIG. 1;

FIG. 5 is a perspective view, partially broken away, of a rearrangingdevice in accordance with the present invention; and

FIG. 6 is a plan view showing an eight by eight rearranging device inaccordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will now be described ingreater detail with reference to FIG. 1. This figure shows an example ofa representative four by four optical wave guide communicationrearrangement device 10 according to the present invention. The device10 has an input side 12 and an output side 30. A plurality of opticalwaveguide arrays 14, 16, 18, 20 are each fed to the input 12. Eachoptical waveguide array 14, 16, 18, 20 may be formed of optical fibers,such as a ribbon of fiber, individual fibers, fiber cables, or othersuitable array configurations, such as optical capillary tubes or othersuitable waveguides. Each input array 14, 16, 18, 20 is connected to arespective microprocessor, fiber ribbons or other communication deviceor medium (not shown). The array 14 is split into individual waveguidesor fibers 14 a, 14 b, 14 c, 14 d. In the preferred embodiment, opticalfibers are utilized and each of the individual fibers 14 a-d is fed to arespective output fiber array 22, 24, 26, 28. For example, the fiber 14a is fed to the output fiber array 22. The fiber 14 b is fed to theoutput fiber 24. The fiber 14 c is fed to the output array 26 and thefiber 14 d is fed to the output array 28. The remaining input fibers 16,18, 20 are routed similarly to the fiber array 14. The fiber 16 a is fedto the output array 22. The fiber 16 b is fed to the output array 24.The fiber 16 c is fed to the output array 26 and the fiber 16 d is fedto the output array 28. Since the input arrays 18 land 20 are similarlyrouted they will not be described here. The output array 22 thereforecontains the first fiber 14 a, 16 a, 18 a, 20 a of each of the inputarrays 14, 16, 18, 20. Likewise the output array 24 contains the secondfiber 14 b, 16 b, 18 b, 20 b of each of the input arrays 14, 16, 18, 20.Output arrays 26 and 28 similarly contain the third and fourth fibers ofeach of the input arrays 14, 16, 18, 20 respectively.

The input arrays 14, 16, 18, 20 may be defined as any number of m×noptical fiber arrays, with the preferred embodiment having m=1 to formribbon input arrays. The output arrays 22, 24, 26, 28 may also bedefined as any number of r×s optical fiber arrays, with the preferredembodiment having r=1 to define ribbon output arrays. The number ofinput and output arrays may be varied, as can the number of opticalfibers in each of the arrays.

While the preferred embodiment described above provides a perfect“shuffle”, it will be understood by those skilled in the art from thepresent disclosure that the fibers could be routed in pairs or groupsaccording to a specified roadmap depending on the requirements of aspecific backplane communication interconnection arrangement for whichthe rearrangement device 10 is being used. For example, in FIG. 1, thefibers 14 a and 14 b could both go to 22 a and 22 b; fibers 14 c and 14d could both go to 26 a and 26 b; fibers 16 a and 16 b could go to 24 aand 24 b; and so on. Other arrangements could also be utilized, ifdesired.

Referring now to FIG. 2, the fiber end faces of each of the input arrays14, 16, 18, 20 and fiber end faces of each of the output arrays 22, 24,26, 28 are shown. It should be understood by those skilled in the artthat while the arrangement pattern of FIGS. 1 and 2 is shown here, otherrearrangement schemes are possible and within the scope of thisinvention. For example, instead of selecting the first fiber of eachinput array 14, 16, 18, 20 to be a part of the output array 22, onecould arrange the output array 22 to receive fiber 14 a, fiber 16 b,fiber 18 c, and fiber 20 d. Therefore, each output array 22, 24, 26, 28may contain any selection of fibers chosen from the input arrays 14, 16,18, 20.

A first preferred method of assembling the rearrangement device 10 ofFIGS. 1 and 2 will now be described in greater detail with reference toFIGS. 3 and 4. Referring first to FIG. 3, the individual fibers 14 a-dare first gathered and secured to form the array 14. This may beaccomplished by the use of epoxy, heat or UV activated adhesives,mechanical fasteners, RTV rubbers or any other suitable fixingtechnique. These arrays may also be formed of ribbon fibers or othermultifiber cables. The fibers 16 a-d are similarly gathered and securedtogether to form the input array 16. Input arrays 18 and 20 aresimilarly formed. At the output 32, in the first preferred method, allof the arrays 14, 16, 18, 20 are bundled and fixed to each otherutilizing any suitable technique such as epoxy, UV or heat activatedadhesives, mechanical fasteners, RTV rubbers, or any other suitableadhesive or hardenable material. The output bundle 32 is then slicedalong the lines labeled A—A, B—B, C—C to form the output arrays 22, 24,26, 28. Those skilled in the art will understand from the presentdisclosure that the slices could be along different planes, or couldeven be in sections or combinations thereof. For example, the opticalbundle 32 could be sliced into four 2×2 bundles, two 2×4 bundles and two1×4 arrays, etc. It should be understood by those skilled in the artthat each of the input arrays 14, 16, 18, 20 may be formed of ribbonfibers each containing a desired number of individual fibers. It shouldalso be understood that while a four by four rearrangement device 10 andmethod have been described here, these methods are scalable to largerarrays or smaller arrays as required by the particular application, suchas twelve 1×8 input arrays and eight 1×12 output arrays or any otherdesired configuration.

A second preferred method of assembling the rearrangement device 10 ofFIGS. 1 and 2 will now be described in greater detail below. In thesecond method, the resin matrix holding each of the input arrays 14 a-d,16 a-d, 18 a-d and 20 a-d of optical fibers together is partiallystripped or leached away at one end of the arrays. These strippedoptical fibers are then rearranged into output arrays, for example, 14a, 16 a, 18 a, 20 a, etc., using a manual or automated process based ona desired optic fiber roadmap for the interconnection outputs. Eachoutput array is then separately bonded or adhered together, and thestripped fibers can be re-ribbonized, if desired. This provides theadvantage of being able to form the rearrangement device 10 with ribbonlegs of any desired length which can be used to interconnect backplanecomponents regardless of spacing and without the need for splices.

Referring now to FIG. 4 a cross-sectional view of a rigid enclosure 40for housing the rearrangement device 10 is shown. The package 40 may beeither cylindrically shaped or rectangularly shaped and may have variouscross-sectional areas depending upon the number and shape of the fibersin the bundle 32. Beginning at the input opening 42, the central bore 46is profiled to have a lead in section 50. The lead is section 50 mayhave a circular, oval, rectangular or other suitable cross section. Ashoulder 52 is formed between the lead in section 50 and a transitionsection 48. The transition section 48 has a smaller cross sectional areathan the lead in section 50 and may be of a circular, oval, rectangularor other suitable shape. A second shoulder 49 is formed between thetransition section 48 and retention section 47 of the bore 46. Theretention section 47 is dimensioned to snugly receive the plurality ofinput arrays 14, 16, 18, 20. Since the output side of the enclosure 40beginning at the output opening 44 is symmetrical to the portiondescribed thus far, it will not be described in further detail. Itshould be understood however that the enclosure may be modified so thatthe output section is not symmetrical to the input section. Theenclosure may be optionally equipped with through holes for mounting toa system component such as a rack. Alternatively, other attachment meanscould be provided such as a Velcro® hook and loop fastener, or anadhesive for securing the enclosure 40 to a rack or other components.

Those skilled in the art will also understand from the presentdisclosure that an enclosure 40 can be molded or cast from a resinmatrix directly about the bundle 32. The function of the enclosure is tohold the optical fibers firmly and stably in position in the transitionarea between the ribbons of the input arrays and the ribbons of theoutput arrays in order to prevent damage to the individual opticalfibers in the transition area.

The rearrangement of the input arrays 14, 16, 18, 20 is represented inFIG. 5 to illustrate the three-dimensional rearrangement that takesplace as the fibers of each input array are rearranged in a confinedspace. The housing 40 preferably includes flexible boots 54 located ateach end to act as a strain relief for the input and output arrays. Anadhesive, such as an epoxy may be located in the housing 40 to firmlyhold the fibers in position in the rearrangement area to prevent damageto the optical fibers.

Referring now to FIG. 6, an alternate enclosure 140 is shown inconnection with an eight by eight rearrangement device 110. Therearrangement device 110 includes eight input arrays 114-121, and eightoutput arrays 122-129. The alternate enclosure is made of a braided orwoven sleeve that is installed over the rearrangement area of theinterconnection device, and is preferably impregnated or filled with anadhesive matrix, such as RTV silicone, to hold the optical fibers in therearrangement area in firmly and stably in position. One preferredsheath is a VARFLEX sheathing, type HP which is flame retardant.However, it will be recognized by those skilled in the art from thepresent disclosure that other sheath types of other materials andconfigurations can be used.

While the present invention has been disclosed in the context of thepreferred embodiments utilizing optical fibers, it will be understood bythose skilled in the art from the present disclosure that it could alsobe used in connection with plastic optical fibers or other waveguidematerials, such as a leached fiber bundle or hollow capillaries.

An advantage of the present invention is that a large array of inputfibers may be rearranged into various arrays of output fibers thatcontain selected ones from each of the input fibers. These rearrangementtechniques can be used to create cross connects, optical switches,backplanes or in any application that requires optical fiber routing ina very small space due to the three-dimensional rearrangement of thefibers in the rearrangement area. For example, in the embodiment shownin FIG. 6, the sheathing which forms the housing 140 is onlyapproximately two inches long and 0.16 inches in diameter. The housing40 of the first embodiment is also approximately two inches long andapproximately 0.5 inches in diameter, allowing for positioning of therearrangement device 10 in confined spaces.

While the preferred embodiments of the invention have been described indetail, the invention is not limited to the specific embodimentsdescribed above, which should be considered as merely exemplary. Furthermodifications and extensions of the present invention may be developed,and all such modifications are deemed to be within the scope of thepresent invention as defined by the appended claims.

What is claimed is:
 1. An optical rearrangement device comprising: aninput side including at least first, second and third separate, flexibleinput light guide arrays, each of the arrays including a plurality oflight guides, an output side in which the light guides of the at leastfirst and second input light guide arrays are repositioned to form atleast first and second separate, flexible output light guide arrays witha first one of the light guides of the first input light guide arraybeing repositioned to extend into the first output light guide array, asecond one of the light guides of the first input light guide arraybeing repositioned to extend into the second output light guide array,and a first one of the light guides of the second input light guidearray being repositioned to extend into the first output light guidearray and a second one of the light guides of the second input lightguide array being repositioned to extend into the second output lightguide array, and a light guide of the third input light guide arraybeing repositioned to extend into one of the output light guide arrays,an enclosure having an input opening and an output opening from whichthe input and output light guide arrays extend located between the inputside and the output side which contains a non-planar, three-dimensionalrearrangement area having a thickness defined by at least three lightguides that cross over one another at approximately the same point asthe light guides are repositioned, and an adhesive located in theenclosure to hold the light guide arrays in position in therearrangement area.
 2. The optical rearrangement device of claim 1wherein the light guides comprise optic fibers.
 3. The opticalrearrangement device of claim 1 wherein the first plurality of lightguide arrays are a plurality of ribbon fibers.
 4. The opticalrearrangement device of claim 3 wherein each ribbon fiber represents oneof the fiber arrays.
 5. The optical rearrangement device of claim 1wherein the second plurality of light guide arrays are a plurality ofribbon fibers.
 6. The optical rearrangement device of claim 5 whereineach ribbon fiber represents one of the fiber arrays.
 7. The opticalrearrangement device of claim 1 wherein the enclosure is made of aflexible material.
 8. A method of rearranging a plurality of opticalwaveguides comprising the steps of: arranging a plurality of opticalwave guides into at least first, second and third separate, flexibleinput wave guide arrays at an input side; rearranging the plurality ofoptical wave guides in a three-dimensional rearrangement area to form atleast first and second separate, flexible output arrays at an outputside by repositioning at least a first one of the light guides of thefirst input light guide array to extend into the first output lightguide array, repositioning a second one of the light guides of the firstinput light guide array to extend into the second output light guidearray, repositioning a first one of the light guides of the second inputlight guide array to extend into the first output light guide array,repositioning a second one of the light guides of the second input lightguide array to extend into the second output light guide array, andrepositioning a light guide of the third input light guide array toextend into one of the output light guide arrays, the rearrangement areahaving a thickness defined by at least three light guides that crossover one another at approximately the same point as the light guides arerepositioned; enclosing the rearrangement area in a housing having aninput opening and an output opening from which input light guide arraysand output light guide arrays respectively extend; and holding theoptical waveguides stably in position in the rearrangement area.
 9. Themethod of claim 8, further comprising ribbonizing the output lightguides to form the output light guide arrays.